中文摘要：

选取季节性河流大沽河上、中、下游3处代表性河床的沙样作为试验样品，采用张力计法测出不同沙样的脱湿和吸湿过程，采用Van Genuchten模型拟合不同沙样的水分特征曲线，利用MATLAB中的Nlinfit函数求得Van Genuchten模型参数。结果表明：土壤水吸力（水银柱高度）为0-10cm时，沙样的质量含水率变化明显，随着土壤水吸力逐渐增大，质量含水率逐渐降低，当土壤水吸力为60cm左右时，含水率变化减缓，逐渐趋于平稳；3种沙样均存在水分特征曲线滞后现象，粗沙的滞后现象较细沙的明显；实测水分特征曲线和拟合曲线基本吻合，Van Genuchten模型和MATLAB求参方法均适用于拟合季节性河床沙样的水分特征曲线。

英文摘要：

Typical riverbed sand samples collected from the upstream, midstream and downstream of the seasonal river of Dagu River was used to determine the dehumidification and moisture absorption processes of different sands by using the tonometric method. The Van Genu- chten model was used to fit the moisture characteristic curves of different sands and the Nlinfit function in MATLAB was used to calculate the values of θ, θ, α and n of the Van Genuchten model. The results show that the sand moisture content changes significantly when the water suction pressure is between 0-10 cm water column; the sand moisture content decreases as the suction pressure increases; when the suction pressure is about 60 cm water column, the change in moisture content becomes insignificant and is gradually stabilized; the moisture charac- teristic curves of the three sand samples show hysteresis, and it is more obvious in coarse sand than that of in fine sand. The theoretical resuits fitted well with the measured curves and fitting curves, which indicates that the Van Genuchten model and the MATLAB method are suitable for fitting, the soil water characteristic curves of seasonal riverbed sands.